The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Hybrid powertrains typically include a first torque generator, such as an internal combustion engine (ICE), and a second torque generator, such as an electric machine (EM). Each can provide torque to a driveline to propel a vehicle. Various configurations of hybrid powertrains can be used, including a strong hybrid powertrain and a mild hybrid powertrain. In a strong hybrid powertrain, the EM can drive the driveline directly, without transferring torque through a component of the ICE.
In a mild hybrid configuration, the EM is coupled with the ICE, such as through the front end accessory drive, whereby torque generated by the EM is transferred to the driveline through the ICE. An exemplary mild hybrid powertrain includes a belt alternator starter (BAS) system. In the BAS system, the EM is coupled to the ICE via a traditional belt and pulley configuration, which drives other accessory components including, but not limited to, pumps and compressors.
Powertrain torque control typically includes two torque control domains: axle torque and propulsion torque. In a mild hybrid powertrain, the propulsion torque is the output torque at the crankshaft of the ICE, which includes the EM torque contribution. Axle torque includes torque output from the driveline.
Powertrain systems include several torque features, each of which seeks to influence the amount of drive torque at various points along the powertrain system. The vehicle's driver, who commands a desired output torque from the torque source(s) or a desired axle torque, is an example of an upper level, or global, torque feature. Exemplary driver inputs include, but are not limited to, an accelerator pedal and a cruise control system.
Modern powertrain systems include additional torque features or torque requests such as vehicle stability control systems, traction control systems, engine overspeed protection systems, transmission shift quality systems, engine and/or transmission component protection systems, and/or driveline component protection systems. The torque features can number in the tens to over a hundred, depending upon the particular configuration of the powertrain system.
The torque features of a particular powertrain system are independent and can often seek to control the drive torque at the same time. Because the powertrain system can only produce a single drive torque value at any time, an arbitration system determines the correct drive torque to produce. A control module is typically provided for arbitrating the multiple torque requests. In a hybrid powertrain system, this control module is responsible for arbitrating torque requests for a plurality of torque generators (e.g., the ICE and EM).